Holley's Great Defect By Omission - Or, How To Fix That Mysterious Off The Line Stumble

While the 4150 is by far the most popular carb for serious street and strip performance it has one universal issue that can play havoc with your cars 60 foot performance. Here's the rundown on secondary jet extensions and why every Holley carb should be automatically fitted with them.
#classiccar #musclecar #carburetor
MERCHANDISE:
Get Your UTG T-Shirts Here: uncletonysgarage.com/product/...
Get Your UTG Stickers Here: uncletonysgarage.com/product/...
OUR STORE: uncletonysgarage.com
*SOCIAL MEDIA:
Facebook: / uncletonysgarage1

[@MikeBrown-ii3pt]

I'm definitely not a newbie to carbs and you'll never hear me complain about carb videos. As a matter of fact, the more the better. I'm often reminded of little tricks that I've forgotten over the years. I didn't forget about jet extensions but, there have been other things.

[@The_R-n-I_Guy]

Fuel injection is pretty good. But I'm ready to simplify my life. I want a carburetor, points ignition and a manual transmission. No electronics. Not even electronic gauges. I'm sick of sensors and wires.

[@Bill_N_ATX]

Amen! And a one wire alternator too.

[@echota23]

Ultimately emp proof

[@superduty4556]

@@echota23 emp goes off and we have much bigger fish to fry than enjoying a classic car starting.

[@Ecosse57]

@@superduty4556 bugout vehicle.

[@echota23]

@@Ecosse57 yep and everyone else is walking

[@moedog07]

Uncle Tony spends his time and effort to give his FREE carburetor knowledge away in his videos, and people complain. Shaking my head. Keep preaching knowledge UT. 0:03

[@Sam-zp5rd]

Man I wish I knew that 30 years ago. I fought a stumble of the line with bigger accelerator pumps, and float levels but never could get it right.

[@omeyehead7436]

I had a dodge magnum with this problem. It was frustrating.

[@paulbruno8327]

You’ll never hear me complaining about too many carb videos! Thanks again for another great video UT!!! 🏁

[@pete540Z]

Thanks, Tony. Damn, we're old (I was born in Apr 1962 - I think you were born in 62). I remember jet extensions and use them. Its wild to me that people wouldn't know about them!

[@allhailinternalcombustion]

Well you have to remember that there are 2 generations or so that were born in the days of fuel injection. Those poor people.......lol. And most of us that are older had a few head scratching moments trying to figure that bog out until we talked to someone.....in person......at a speed shop, or a magazine came out with carb tech.

[@pete540Z]

@@allhailinternalcombustion totally agree. FWIW, I'm converting the 406SBC in my 240Z to TBI EFI, replacing the carb.

[@HeadFlowInc]

Jet extensions also require a notched float in the rear bowl. Highly recommended upgrade! 👍

[@christophersambuco9414]

I have an idea for an awesome carburetor tuning video (or even a little series of videos)... Install a wide band O2 meter, and do some real time test runs, and then show the methods to get the air fuel ratios right for hard acceleration throughout the RPMs, light acceleration and cruise. That would be some excellent content. 👌

[@herbnalis3723]

This has happened. Chevy Hi-Performance magazine did an article with a lap top/data logger/wide band sensor & drove & fine tuned the carburettor.

[@josephsperrazza3082]

Tuning Carbs Brings Back Memories Of My Days As Young Kid Goose It And Masher , My Job Was Lay Across The Engine Bay With A Screw Driver And Yell Goose It Masher ,Never Had Problems With Bogg Outs Off line.

[@89ddx]

The drag race specific 4150s like the quick fuel carbs come with extensions. The other possibility that can cause problem is fuel slosh from the front bowl through the breather tube over the top. The solution is to add breather extensions into the bowl and to run a piece of hose from one breather tube to the other with a small slit in the top for air to get in. Fuel has to go much farther to slosh in

[@thisisyourcaptainspeaking2259]

What I like about carburetors most is I can go through one on a picnic table if need be. I prefer spread bore carbs. The best fix for any Holley is a Thermoquad.

[@340duster8]

I had to put a edelbroken on my Duster so I could rebuild the thermoquad. I did not realize on how badly it needed a full clean and rebuild until I changed carbs.

[@glennmanchester5696]

Or a quadrajet I am a gm guy so my go to is the quadrajet I knew guys w mopars and even they didn't really care for the thermoquad

[@340duster8]

@@glennmanchester5696 the quadrajet and thermoquad is a love/ hate relationship. The bad about the thermoquad is the bowls crack real easy.

[@scottbrazinsky615]

Really admire this gentleman.The exact held true in 1982, as he explains here.Thank you sir.

[@lowluv72]

I can never get enough of these pre computer carb and ignition videos

[@mrkrzt]

Love your knowledge. Old school thing.. I know the only time I learned something was a mistake and figure out why. No plug in scanner just experience

[@racerx7319]

THANKS TONY I LEARNED SOMETHING I DIDN'T KNOW.

[@benwamsley5876]

This is why I never miss an episode of utg!

[@MrDibbons]

Back in the '70's I made sure to use the jet extensions in my 600 CFM Double Pumper (common procedure back then). Of course, launching a 4 speed @ 6,000 RPM with a 4.56 rear end ratio helped a lot to eliminate any chance of bog anyhow.

[@NeverMetTheGuy]

I don't even own anything with a carb, and still show up to this shit. It's just fantastic information.

[@haatch999]

hey something incredible is streetmachineTV is having this exact problem they thought it was heat soak or other things always bogs nearly dies at 10 ft mark then can run whole track rippen this video has helped so much already your the man tony

[@frankc1430]

Excellent! More old school carburetor stuff.

[@timothyarnott3584]

Hey Tony, Tim here, yea, jet extensions for the secondary bowls is ESSENTIAL!!.....certain carb manufact. Know......my expensive QFT 950 for my Poncho, has them already!!.....essential for yer 60 ft......AED/QFT, offers carbs with extensions....NO FLOAT height band-aid......get a float relieved for them........GOTTA have them!!!......

[@HomeTipsAndTricks]

The carb videos are just great. I Thought I had a handle on Holleys. Your info is just plain great stuff! Thanks UT!

[@moyadapne968]

Uncle Tony has his Support The Pill T shirt on.

[@anthonyjackson280]

Strong parallel with "Miss Shilling's orifice". For those unfamiliar, it is a great story of what today would be called 'a hack' but it greatly ameliorated a deadly carburetor design flaw in 1940.

[@craighansen7594]

A message to the ones complaining about too many videos on carbs. Even if you think you know it all, if you listen to another's take on things, you might learn/ re-learn something.

[@brianalbrecht4423]

U.T....never stop with carb videos ....!..the more info u put out there the more people will stay with carb's insted of e.f.i....GREAT video....thanks ...Brian

[@johndoe43]

If anybody cries or whines about your videos or content they have big problems. You always have good info with good delivery and intentions. As always thank you for your efforts

[@MrJohnnyDistortion]

I get all choked up and feel fat whenever U.T. talks about carbs. 🤣😆

[@CAROLDDISCOVER-FINDER2525]

Thank you. I was never the carburetor man I guess lack of patience and desire. And the fact that my dad was great at it. Anyway he would dent the floats repair the floats if needed and put on his homemade jet extensions. So you're right forgotten knowledge. In my case I didn't ask when I had the opportunity to learn. But I gave racing up long time ago. But I've got my son's 57 Chevy sitting out here and his brother and I are going to put together and make at least one run down the quarter. Thanks for the update / reminder. It's just like on the channel when they called in the expert old guy to set the dwell on a set of points. As they said the laptops to one side and watch in amazement.

[@blackcoffeegarage]

"You learn something new every day"... yeah, you do if you watch Uncle Tony! Wow!

[@strokermaverick]

U.T. Great upload! Good info! Holley has been in the business, for thousands of years. That made me chuckle!

[@edge2sword186]

Remember ,Sam Colt made all men equal . Holley is Colt industries and they go way back before the autos were made.

[@williamcharles9480]

Good job, Tony. Getting the average guy to understand carb theory is an art unto itself. Uncle, you are an artist.

[@victormiranda9163]

the first Carb Vid that made sense to me.

[@uasparts]

Yet another awesome carb tech instructional from uncle Tony! Great stuff, I’m 46 and quite advanced with carbs, but I learn something from every one of these videos just from the standpoint of performance.

[@camaroguy2919]

You have mentioned this before briefly in another video. Thnaks for going into detail after your explination I can see how easy that would be to miss and throw money at the wrong area of the car.

[@charlesgall7829]

Thank you. Priceless info not found in Holley books.

[@thomasreaves588]

Once again, Thank you for sharing this wisdom of yours!

[@kainhall]

ive also seen people use the wrong type of gasket on the power valve.... dude is just enriched the whole time LOL fixed that and rebuilt the card...... ended up with a LOYAL customer . im 28 and work in a 3 person CO-OP shop in NE montana...... not that many people left who know how (and want to) work on these older outfits . my favorite thing is using a vac gauge to tune for highest vac (idle mix and timing) for "granny driven" cars.... it just makes them run so smooth, with very little stalling and hesitation when cold . got quite a few LOYAL AF! customers that way . . . gotta love people who dont know GM made a 366 also LOL a 454 type block.... but only 366 cubes AKA indestructible (because of low power, yet WAY WAY overbuilt/strong/thick internals) . but VERY little info (or conflicting info) on the internet about them good thing i get old "tune up" books from the 50s to the 80s for my B-day and X-mas LOL i HORD thows old books lol

[@jonathanbush5024]

To add a note about vacuum secondary holleys. Holley makes a $60 lit to replace the jet plate with a metering block allowing for different jetting. The part number is 34-13.

[@shoominati23]

I've run roadrace cars where we fit the double-wedged floats and those jet extensions, also we join the 2 float vents together with one of those offroad vents with the holes in the top.

[@brianhdueck3372]

Always good info from UTG. Thank you sir.

[@roadrunner4404]

Once we added ext tubes to the rear jets. Did it on a whim. The float couldnt drop down enough n it ran out of fuel at the top of second gear. Yes they make floats with twin cutouts but we took the ext off. Boss sold the car. Mild 350 in a vegan. 9 in slicks.

[@SPEEDOFDOG]

Now this here is pure gold!

[@fairlanephantom]

Thanks again for your invaluable input Uncle Tony. I'm just running a Holley 2 BBL on my Ford V8 292, so I'm not taking my car to the track, but every bit of knowledge you share is great to keep in the back of my mind. On my car it had one plug that was getting hot, so I backed off the timing, I thought to balance that slight hesitation I ended up with at the accelerator pump adjustment on the adjustment at the throttle. Still had it, so I'm going to bring it up again. I have a small crack in the exhaust manifold that i think leans that cylinder out. One of the part carburetors i bought had an off road spring that I added to my carb. I've seen two schools of thought first said to make the float level, the other said to set the fuel height to a quarters diameter from the brim of the carb. Quarters width has worked much better, straight would flood every few trips. But anyway, I think that slight bump in the ignition timing can smooth things out as well. Just from the 10 -12 range I've been in makes a big difference. From a dead stop.

[@joew8440]

You have a great way of breaking things down. You always make perfect sense

[@smilsmff]

yep they made a race kit at one time for all of that. and i used Fuel bowl extensions

[@bigone721]

Not sure this is a forgotten thing. The last few 4 barrel carbs I've bought from Holley have come with jet extensions in a bag in the box.

[@speedy_pit_stop]

IOW it's optional. There must be a downside to using them on the street.

[@jonmoore8995]

Love Old School stuff. Got a lot from this.

[@nitrometh42]

I wish I knew this back in 1989....the last time I did any type of racing.....bogging off the line. Bracket racing, High school class.

[@ShakeYourFist]

Cool and simple stuff that first timers need to know. You forgot to explain the vent whistles. I have been running a 3x2 setup for years, so I never needed the jet exentions. I have the vent whistle on the centre carb though.

[@jhonditch4269]

dad had a hell of atime trying to get a holley to work right never had a problem with carters

[@malibuStroker]

The carb videos are awesome!!!

[@TheCanadianBubba]

Just got my first 750 ! Thanks Uncle Tony 👍

[@tommyhawks856]

Another excellent video, Tony.

[@hugechimp]

Ignore the haters. The carb vids are Fantastic! TY, Tony.

[@craighansen7594]

Don't forget, as you seriously increase your ability to create G forces on your launch, you better make sure your oil pan sump can handle it. Hard launch, awesome! Oil starvation at launch, burned rod and main bearings ☹!

[@johnpena9165]

That's why higher capacity oil pans are recommended for drag racing !

[@speedy_pit_stop]

UTG had a video about this just last week i think.

[@johntierno546]

Some of the old school drag racers back in the 60s figured out how to battle this by mounting the carburetors sideways

[@sterlingbeck5247]

Good stuff Uncle Tony! I love the carb videos!

[@donaldshidal851]

I got so disgusted with Holley and their tech support, blown powervalves being replaced on the side of the road, hot intake manifold boiling the gas that spills out, glove box of powervalves and gaskets. I came to understand it as a POS. Went to an AFB, never looked back. Set it and forget it. Thanks Uncle Tony

[@juniorwhelchel6337]

I'm so thankful for you and your videos I'm learning tons from you I'd love to know u personally wish u were closer to me here in Gaffney SC thank you UNCLE TONY

[@KoryBrooks]

I have used power blast plates on the squirters on the last Holley I had and it was pretty awesome but I should have had jet extensions too.

[@moparmatt5896]

This is why I love your videos! The little tips and tricks

[@Hogiewan1]

Great info especially for an old timer like me. Many thanks

[@fireballxl-5748]

Great info. Thank you UT.

[@MsKatjie]

thanks for the valuable info., Uncle Tony . cheers

[@mrkultra1655]

Thanks Tony. Just goes to show you how many things can be fixed with a small piece of copper pipe.

[@donaldhalls2189]

Awesome, hope you had a great Christmas and wishing you all the best in the New Year

[@Z_732]

Yep... Good stuff UT.. thanks for the upload!

[@ram2500pikup]

Thank you UTG!

[@autonomous_collective]

AED PERFORMANCE Holley Carbs has been selling these extensions and more, for years. In my opinion, the AED Holly carbs are the best on the market. Check out their kits and carbs.

[@sydrider6023]

Nice subject to learn from, thanks and Happy New Hot Rod Year!🎉

[@benjaminmorgan6]

The carburetors that I use, thanks for the lesson

[@calvinmiller8714]

Great video good job 👏

[@Jonhobbs64]

I recently bought a Holley HP 1000 carburetor and it had a small ziplock bag with jet extensions in the box and I had no idea what they were for. Now I know!! Thank you for all the killer explanations and knowledge! I'm going to take a look at my Holley carburetor book I bought 25 years ago and see if there's any mention of jet extensions.

[@rapdaddy2642]

Good info as always .. thank you

[@stevenkirk2563]

Cheers UTG I learnt something new.

[@zAvAvAz]

YesH thanks for this Uncle !

[@Charles_S.]

Great tip Tony👍

[@jontg429]

Alright Tony, time for a curve ball, now do a video on rebuilding Zenith Stromberg carbs off an MG lol. Good video, love watching the carb vids!

[@TinManKustoms]

In circle track race cars we used to have the same problem but alot of guys I knew made extensions that went to the right so it would continue to get fuel throughout the g forces of curve. I've even gone as far as making a t extension for my off road truck to prevent fuel starvation. Along with modified fuel floats that had weights in them

[@markszczepaniak5888]

Uncle Tony love to see how you would select the correct size power valve on primary side on a automatic transmission car, with actual vacuum at idle. Love to see your experience in action, on holley carburetors. Thankyou for last one, I enjoy this subject.

[@jacksonbermingham2168]

i think they do it in drive with engine warmed up. then check vacuum reading.. need a mate so don't get run over. id probably block the brake booster line to.. so u can jam the brakes on and hand brake and still hold it in gear and not have a vacuum usage at the booster so u can get correct vacuum reading

[@isingthebodyelectric1041]

Interesting video as always Tony. I always learn something new. I wanted to bring up that efi can also suffer (I’d argue worse) from fuel slosh when not plumbed to a baffled tank or gravity fed inline pump(s).. Not an issue with oem equipped vehicles but, this is a situation the inexperienced can easily find themselves in when converting a carbureted vehicle over to efi. Especially, when using one of the readily available aftermarket efi units as these kits often include a cheap inline pump which encourages the customer to try and retain their stock fuel tank. To keep things short and to the point. Both fuel systems have their advantages/disadvantages but, my experience with efi is you’ll pay more to make it right.

[@BigT27295]

Good stuff Big T...

[@meh_name_j3ff120]

Ah yes carburetors

[@EverythingHorsepower]

I’m a bit surprised you didn’t mention that you need a float that is notched for the jet extension

[@AUTOIGN]

Great to know, I always thought Holleys were the best have had a 600 vacuum sec, 650 dual feed double pumper and a 780 Q-jet replacement, but never knew. Being a Mopar man do you think Carters are better, why even have a carb vs injectors these days. Keep it coming , just found your channel and love it.

[@77zrod46]

Good info. Thanks.

[@jdsimons6115]

Mine was a lean stumble soon as it opened and before the truck launched (C1500 chevy) this was confirmed with an AFR wideband. I did a couple of things, my fuel level is set to the middle of the sight glass in both bowls (4150 "brawler") Put .040 accelerator pump nozzles and put washers under the acc. pump adjustment springs to stiffen them up and the intake flange is angled forward a bit so it levels out better when the front end lifts. This cured 90% of it still stumbles a hair if i open it 100% from a dead stop. Havent gone to the extensions/floats still run the power valve.

[@chrishensley6745]

One thing I would like to add Tony...Great job on this,,,,is I run 4 cars with carbs still and even running todays 93 non ethanol gas..100 percent they say...I have learned the last few years on mine and other peoples carbs to run the bowl level a little lower than norm due to even running so called 100 percent gas,it is not and the gas grows with heat unlike years ago will overun float addjustment and make it override and load up after driving on a Hot day....Love your channel and you have been there for sure.

[@mudduck754]

Ahh the controlled fuel leak known as Holley.. always good for a under the hood fire... Never had problems with the thermal quads, never had problems with the quadrajet, never had problems with a Carter. Because they don't have little o-rings that connect the feeder tube to the float bowls. The only carburetor I've ever had where the secondary float would stick and dump gas all over the engine. And after a under the hood fire that destroyed everything last year. My dumbass went and bought another brand new Holley on it. The old one was in 1974 model so yeah it was due to have a few problems. But easy to work on alongside the road I keep a package of them little o-rings in my sun visor.

[@robertkoontz7865]

Another great tip Tony, They should consult with old school hot rodders like yourself. Looks like it needs a re-design. Pre-fill a bowl? A Launch Bowl. lol

[@togst]

Interesting subject and another great explanation. I bought a classic car a year ago after being tempted by how they were supposed to be simpler to understand and work on. For the most part that has been the case, but the carburetor has given me grief from day one. I'm considering converting to fuel injection in order to "set and forget", as the constant tinkering is getting annoying.

[@jimjungle1397]

It's been a while but I seem to remember the jet size is recommended to be slightly increased when using jet extensions. Also I think the jet extensions might only fit with certain floats, brass maybe, maybe not plastic, side hung floats. I'm not sure. With a Six-Pack, no need for jet extensions.

[@Adrenacyde]

I always switch to the Nitrophyl floats when I do the Jet Extensions

[@jimjungle1397]

@@Adrenacyde At one time I had some sort of plastic floats that had reliefs in them for the extensions.

[@bobs2528]

Hey Tony ! Another great article . Only one thing . Doesn`t the float need to be notched for clearance ? The notches would insure full travel of the float , of course effecting the needle and seat opening fully . No ?

[@mattsgarage6670]

Just purchased a QuickFuel 750 brawler has the extentions from the factory kind of cool

[@shanerorko8076]

I'm happy with carburetor videos. I'm a mechanic by trade but I'm 34 so 99% of cars I work on are fuel injected. My daily is a Mitsubishi ute (Australian here) and it is carburetted but the Mikiuni that was on it was crap so I installed a Webber I think it's a 32 36 mech secondary and I have never had an issue. So I've never had to fix my carby, I did try and lean it up a little on accel drilling out the air bleed but it didn't really change so i left it.

[@felisconcolor1112]

Hi Tony: could you add a little more to Holley carburetor lore with a talk about the power valve blowout preventer, and installation for same? I remember when, in the '80s, a couple of the hot rodding magazines were talking about a new DIY kit which protected the power valve from blowing out during backfires, and was available at a very nice price. It appears sometime in the 90s Holley bought the patent(s) and have standardized the feature across its model line, but there are easily tens or maybe hundreds of thousands of Holley carburetors out there which could benefit from adding that simple kit.

[@daverosinski3663]

I replaced the power valve with a blank and raised the jet size, but never knew about the jet extensions. It didn't stumble, but probably ran a little lean.

[@worldofwoodchip]

Thank you UT been having this problem with a 4160. I don't have 1 million horsepower, just 4 back tires and a deep first gear. Need to see if the extensions will work with side hung bowls. If not I'm not opposed to switching to 4150 bowls

[@worldofwoodchip]

It is a Quick Fuel, it has a metering plate that uses jets

[@patrickradcliffe3837]

11:57 Money, Money, Money Tony. They would have to retool and have two different valve bodies for the double pumpers.